Joint structure and method of manufacturing joint structure

ABSTRACT

A joint structure comprises a light-absorbable member having at least one opening portion and a light-permeable member superposed on the light-absorbable member so as to cover the opening portion, wherein a first annular weld part is formed so as to enclose the opening portion and join the light-absorbable member and the light-permeable member, and a second dot-like weld part(s) joining the light-absorbable member and the light-permeable member is/are formed in a position adjacent to the first weld part.

This application claims priority to Japanese Patent Application No.2016-194254, filed on Sep. 30, 2016, the contents of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

This invention relates to a joint structure comprising alight-absorbable member and a light-permeable member superposed to eachother and joined to each other through a weld part(s) formed in aboundary face or in the neighborhood of the boundary face and a methodfor manufacturing the joint structure.

RELATED ART

As a method for joining plural members has hitherto been known a joiningmethod through laser beam irradiation. In recent years is noticed alaser transmission welding method in which heating is local and thermaldamage to a product is small and an influence of a weld part on anappearance is small. This method is a method wherein a member having apermeability to a laser beam (light-permeable member) is used as ajoining member and a member having an absorbability to a laser beam(light-absorbable member) is used as the other joining member and thesemembers are superposed to each other and exposed to a laser beam fromthe light-permeable member at a pressurized state, whereby energy of theirradiated laser beam is absorbed by the light-absorbable member in theneighborhood of a boundary face thereof to cause heat generation, andthe generated heat is transferred to the light-permeable member to fusethe both members, and finally the fused portions are cooled andsolidified to join the both members to each other.

The laser transmission welding method has some important points. Amongthem, it is especially important that the members to be joined aresurely adhered to each other by pressurization. If a gap is existentbetween the members to be joined, heat generated in the light-absorbablemember by the laser beam irradiation is not well transferred to thelight-permeable member, and hence poor welding such as upheaving,expanding, explosion or the like is caused by local temperature rising.

In general, the pressurization is attained by a method wherein a glassplate having a permeability to a laser beam is disposed onto thelight-permeable member and a pressure is applied to the both membersthrough the glass plate (see Patent Document 1). However, this methodhas a problem that the glass plate is contaminated with soot generatedin the heating and fusion of the members to be joined or a vaporizationingredient of a flame retardant to increase an absorption rate of theglass plate to the laser beam and hence the glass plate itself is heatedto cause breakage. Also, the laser beam is shielded by the contaminatedglass plate so as not to reach to the light-absorbable membersufficiently and hence the decrease of welding strength is caused.

On the other hand, Patent Document 2 proposes a method of adhering themembers to be joined to each other by sucking without using the glassplate. In the method of Patent Document 2, a groove portion is formed inone of the members to be joined and the both members are adhered to eachother by depressurizing a space of the groove portion. In the weldingthrough laser beam irradiation, however, thermal deformation is causedin one or both of the members to be joined or warping is caused in themembers to be joined during the forming, and hence a gap is generatedbetween the members to be joined to decrease an adhesiveness by sucking.

PATENT DOCUMENTS

Patent Document 1: JP-A-562-142092

Patent Document 2: WO2010-035696

SUMMARY OF THE INVENTION

It is, therefore, an object of the invention to provide a jointstructure suitable for uniformly and surely adhering members to bejoined to each other without using a glass plate and to provide a methodof manufacturing a joint structure which is capable of uniformly andsurely adhering members to be joined to each other without using a glassplate.

In order to solve the above problems, the invention provides a jointstructure comprising a light-absorbable member having at least oneopening portion and a light-permeable member superposed on thelight-absorbable member so as to cover the opening portion, wherein afirst annular weld part is formed so as to enclose the opening portionand join the light-absorbable member and the light-permeable member, anda second dot-like weld part(s) joining the light-absorbable member andthe light-permeable member is/are formed in a position adjacent to thefirst weld part.

In the joint structure according to the invention, the light-permeablemember is preferable to be formed into a thin sheet adhering to thelight-absorbable member by deforming at a depressurized state of aninterior of the opening portion before the formation of the first weldpart.

It is preferable that the light-permeable member is rendered into athickness adhering to the light-absorbable member by deforming when theinterior of the opening portion is depressurized to not less than −80kPa but not more than −20 kPa as a gauge pressure before the formationof the first weld part.

Alternatively, the light-permeable member is preferable to be providedoutside the first weld part with a thinned piece adhering to thelight-absorbable member by deforming at a depressurized state of aninterior of the opening portion before the formation of the first weldpart.

In this case, it is preferable that the thinned piece is formed in athickness adhering to the light-absorbable member by deforming when theinterior of the opening portion is depressurized to not less than −80kPa but not more than −20 kPa as a gauge pressure before the formationof the first weld part.

Furthermore, the thinned piece is preferable to be formed along aperipheral edge part of the light-absorbable member.

In order to solve the above problems, the invention is a method ofmanufacturing a joint structure which comprises superposing alight-permeable member onto a light-absorbable member having at leastone opening portion so as to cover the opening portion, irradiating alaser beam from the side of the light-permeable member to form a firstannular weld part so as to enclose the opening portion to thereby jointhe light-absorbable member and the light-permeable member, wherein asecond dot-like weld part(s) joining the light-absorbable member and thelight-permeable member is formed in a position adjacent to thepredetermined site of forming the first weld part after thesuperposition of the light-permeable member onto the light-absorbablemember and before the formation of the first weld part.

In the method of manufacturing the joint structure according to theinvention, the light-permeable member is formed into a thin sheetadhering to the light-absorbable member by deforming at a state ofdepressurizing an interior of the opening portion before the formationof the first weld part and the interior of the opening portion isdepressurized in the formation of the first weld part to deform thelight-permeable member and the laser beam is irradiated from the side ofthe light-permeable member at a state of adhering to thelight-absorbable member.

In this case, it is preferable that the light-permeable member is formedin a thickness adhering to the light-absorbable member by deforming whenthe interior of the opening portion is depressurized to not less than−80 kPa but not more than −20 kPa as a gauge pressure before theformation of the first weld part.

Alternatively, a thinned piece of the light-permeable member adhering tothe light-absorbable member is formed outside the first weld part bydeforming at a state of depressurizing an interior of the openingportion before the formation of the first weld part, and the interior ofthe opening portion is depressurized in the formation of the first weldpart to deform the thinned piece and the laser beam is irradiated fromthe side of the light-permeable member at a state of adhering to thelight-absorbable member.

In this case, it is preferable that the thinned piece is formed in athickness adhering to the light-absorbable member by deforming when theinterior of the opening portion is depressurized to not less than −80kPa but not more than −20 kPa as a gauge pressure before the formationof the first weld part.

Also, the thinned piece is preferable to be formed along a peripheraledge part of the light-absorbable member.

In the method manufacturing of the joint structure according to theinvention, it is preferable that a suction port communicating with theopening portion and connecting to an external depressurizing device isformed in the light-absorbable member.

In the method of manufacturing the joint structure according to theinvention, it is preferable that the suction port is fused and closed byirradiating a laser beam from the side of the light-permeable memberafter the formation of the first weld part while keeping thedepressurized state in the opening portion.

In the method of manufacturing the joint structure according to theinvention, it is preferable that the interior of the opening portion isdepressurized while feeding a purge gas to the interior of the openingportion.

In this case, the depressurization of the interior of the openingportion and the feed of the purge gas are conducted with a double pipethrough the suction port.

In the method of manufacturing the joint structure according to theinvention, it is preferable that an airtightness test of the first weldpart is performed by measuring a change of a pressure per unit time whenthe interior of the opening portion is kept at the depressurized statesubsequent to the formation of the annular weld part or the interior ofthe opening portion is pressurized or the depressurization andpressurization are performed alternately.

In the method of manufacturing the joint structure according to theinvention, it is preferable that the judgement on adhesion between thelight-absorbable member and the light-permeable member, start of theformation of the first weld part and end of the formation of the firstweld part is performed based on a change of a pressure obtained byalways detecting a pressure inside the opening portion.

In the manufacture of the joint structure according to the invention,the light-absorbable member and the light-permeable member arepreviously joined to each other by the dot-like weld parts to correctwarping resulting from the shaping of the light-permeable member andsuppress thermal deformation of the light-permeable member in thesubsequent formation of the annular weld part being large in the thermalinfluence, so that an excellent adhesiveness between thelight-absorbable member and the light-permeable member by suction can bemaintained.

According to the invention, therefore, the joint structure suitable foruniformly and surely adhering the members to be joined to each other canbe provided without using a glass plate, and also there can be providedthe method of manufacturing the joint structure which is capable ofuniformly and surely adhering the members to be joined to each otherwithout using a glass plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an embodiment of the joint structureaccording to the invention and FIG. 1B is a section view taken along aline A-A in FIG. 1A. FIG. 1C is enlarged view of region I-C in FIG. 1B.

FIG. 2A is a perspective view of another embodiment of the jointstructure according to the invention and FIG. 2B is a section view takenalong a line B-B in FIG. 2A. FIG. 2C is enlarged view of region II-C inFIG. 2B.

FIG. 3A is a perspective view of the other embodiment of the jointstructure according to the invention and FIG. 3B is a section view takenalong a line C-C in FIG. 3A. FIG. 3C is enlarged view of region III-C inFIG. 3B.

FIGS. 4A and 4B are section views of modification examples of a thinnedpiece in the joint structure shown in FIGS. 3A and 3B, respectively.

FIG. 5A is a plane view of a light-absorbable member used in the methodof manufacturing an embodiment of the joint structure according to theinvention and

FIG. 5B is a section view taken along a line D-D shown in FIG. 5A. FIG.5C is enlarged view of region V-C in FIG. 5B.

FIG. 6A is a schematic view of a layout showing the method ofmanufacturing an embodiment of the joint structure according to theinvention and FIG. 6B is a section view showing a suction adhering stepthereof.

FIG. 7 is a schematic view illustrating a pressure control device and alaser beam irradiating device used in the method of manufacturing anembodiment of the joint structure according to the invention.

FIGS. 8A-8D are section views illustrating the sequence of forming anannular weld part by irradiating a laser beam to an annular groove of alight-absorbable member in the method of manufacturing an embodiment ofthe joint structure according to the invention, respectively.

FIG. 9A-9C are a section views illustrating another examples of anannular groove applicable to the method of manufacturing the jointstructure according to the invention.

FIG. 10A is a perspective view of an embodiment of the connectoraccording to the invention and FIG. 10B is a section view thereof. FIG.10C is enlarged view of region X-C from FIG. 10B.

FIG. 11A is a perspective view of an embodiment of the sensor accordingto the invention and FIG. 11B is a section view thereof. FIG. 11C isenlarged view of region XI-C from FIG. 11B.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

An embodiment of the invention will be described with reference to thedrawings below. Moreover, similar members and portions shown in thedrawings are represented by symbols added with a symbol “100” or “200”,and an explanation on overlapping portions is omitted.

FIGS. 1A,1B, and 1C show an embodiment of the joint structure 100according to the invention, in which FIG. 1A is a perspective view andFIG. 1B is a section view taken along a line A-A in FIG. 1A and FIG. 1Cis enlarged view of region I-C in FIG. 1B. As shown in this figure, thejoint structure 100 comprises a light-absorbable member 102 having anopening portion O and a light-permeable member 106 superposed with thelight-absorbable member 102 so as to cover the opening portion O andjoined to the light-absorbable member 102 through a first annular weldpart 104 enclosing the opening portion O. Moreover, the term “annular”means not only a circular form such as a ring but also a continuouslyclosed form (endless form). Therefore, the annular form includes notonly a circle and an ellipsoid but also a rectangle, a polygon and otherclosed forms. The first weld part 104 is formed on a boundary face Fbetween the light-permeable member 106 and the light-absorbable member102. As mentioned in detail later, the first weld part 104 can be formedby irradiating a laser beam from the side of the light-permeable member106 toward the light-absorbable member 102 to cause heat generation,fusing the light-absorbable member 102 as well as the light-permeablemember 106 by the generated heat and solidifying the fused portions.

The light-absorbable member 102 has an absorption rate to a laser beamhigher than that of the light-permeable member 106 and is composedmainly of a thermoplastic resin or a thermoplastic elastomer, which canbe shaped by an injection molding or the like. It is preferable to havean absorption rate of not less than 10% to a laser beam selected fromlaser beams having a center of oscillation wavelength within a range of193-10600 nm. As a laser are included, for example, a carbon dioxidelaser (wavelength: about 10600 nm), Nd-YAG laser (wavelength: about 1064nm), a green laser being a secondary harmonic of Nd-YVO₄ laser(wavelength: about 532 nm), a diode laser (wavelength: about 800 nm, 840nm or 950 nm), an excimer laser (wavelength: about 193 nm) and so on. Inorder to adjust the absorption rate of the light-absorbable member 102,a black coloring agent such as carbon black or the like, a pigment, adyestuff and so on may be kneaded with the thermoplastic resin or athermoplastic elastomer.

As the thermoplastic resin are included, for example, polyamide resin,polyethylene resin, polypropylene resin, polyethylene terephthalateresin, polybutylene terephthalate resin, polyphenyl ether resin,polystyrene resin, high-impact polystyrene resin, hydrogenatedpolystyrene resin, polyacryl styrene resin, ABS resin, AS resin, AESresin, ASA resin, SMA resin, polyalkyl methacrylate resin, polymethylmethacrylate resin, polycarbonate resin, polyester resin, polyphenylenesulfide, liquid crystal polymer and so on. As the thermoplasticelastomer are included, for example, styrene-based thermoplasticelastomer, olefinic thermoplastic elastomer, polyester-basedthermoplastic elastomer, polyurethane-based thermoplastic elastomer,PVC-based thermoplastic elastomer and so on. The thermoplastic resin maybe kneaded with glass fibers, minerals and the like as a reinforcingmaterial.

In the illustrated example, the light-absorbable member 102 is mainlycomprised of a peripheral wall 108 defining an opening portion O and abottom wall 110 closing the lower end part of the peripheral wall 108.The cross-sectional shape of the peripheral wall 108 is substantiallyrectangular, but is not limited thereto and may take any shape such ascircular, ellipsoidal, trapezoidal, polygonal, gourd-shaped and thelike. In the peripheral wall 108 is formed a suction port 112communicating with the opening portion O so as to depressurize aninterior of the opening portion O as mentioned later. The suction port112 may be formed in the bottom wall 110 or a lower end of theperipheral wall 108 is opened without forming in the bottom wall 110 andthe opened port in the lower end is used as the suction port 112.

The light-permeable member 106 has an absorption rate to a laser beamlower than that of the light-absorbable member 102 and is composedmainly of a thermoplastic resin or a thermoplastic elastomer, which maybe formed by injection molding or the like. It is preferable to have anabsorption rate to a laser beam selected from laser beams having acenter of oscillation wavelength within a range of 193-10600 nm lowerthan that of the light-absorbable member 102.

As the thermoplastic resin constituting the light-permeable member 106are included, for example, polyamide resin, polyethylene resin,polypropylene resin, polyethylene terephthalate resin, polybutyleneterephthalate resin, polyphenyl ether resin, polystyrene resin,high-impact polystyrene resin, hydrogenated polystyrene resin, polyacrylstyrene resin, ABS resin, AS resin, AES resin, ASA resin, SMA resin,polyalkyl methacrylate resin, polymethyl methacrylate resin,polycarbonate resin, polyester resin, polyphenylene sulfide, liquidcrystal polymer and so on. As the thermoplastic elastomer are included,for example, styrene-based thermoplastic elastomer, olefinicthermoplastic elastomer, polyester-based thermoplastic elastomer,polyurethane-based thermoplastic elastomer, PVC-based thermoplasticelastomer and so on. Moreover, the thermoplastic resin may be kneadedwith glass fibers, minerals and the like as a reinforcing material.Further, the thermoplastic resin or thermoplastic elastomer may bekneaded, for example, with a white pigment or a chromatic coloring agentof yellow, green, red or the like as long as it has an absorption ratelower than that of the light-absorbable member.

In the joint structure 100, second dot-like weld parts 114 joining thelight-absorbable member 102 and the light-permeable member 106 aredisposed in position adjacent to the first annular weld part 104 asshown in FIG. 1A. The second weld part 114 is formed by irradiating alaser beam from the side of the light-permeable member 106 toward thelight-absorbable member 102. It is important to form the second weldpart 114 before the formation of the first weld part 104. Because thesecond weld part 114 can correct warping due to the shaping of thelight-permeable member or suppress thermal deformation of thelight-permeable member in the subsequent formation of the annular weldpart producing a large thermal influence.

The joining strength between the light-absorbable member 102 and thelight-permeable member 106 can be increased even more by forming thesecond weld part 114 in addition to the first weld part 104.

The second weld part 114 is preferable to be formed adjoining to acorner part when the light-permeable member 106 is substantiallyrectangular. Because the second weld part 114 can suppress thermaldeformation of the light-permeable member 106 effectively in theformation of the first weld part 104.

In the joint structure 100, the light-permeable member 106 is formedinto a thin sheet adhering at its peripheral edge portion to an upperend face of the peripheral wall 108 of the light-absorbable member 102by deforming when an interior of the opening portion O is depressurizedbefore the formation of the first weld part 104. Thus, when thelight-permeable member 106 is superposed with the light-absorbablemember 102, even if a gap is produced between the upper end face of theperipheral wall 108 of the light-absorbable member 102 and thelight-permeable member 106, the interior of the opening portion O can bedepressurized through the suction port 112 to adhere the light-permeablemember 106 to the upper end face of the peripheral wall 108 of thelight-absorbable member 102, whereby an excellent adhesiveness bysuction can be obtained between the mutual light-permeable member 106and light-absorbable member 102 while preventing vacuum breakage due toair leakage together with an effect of suppressing the deformation ofthe light-permeable member 106 by the second weld part 114.

In order to more surely establish the above, it is preferable that thelight-permeable member 106 is deformed when the interior of the openingportion O is depressurized to not less than −80 kPa but not more than−20 kPa as a gauge pressure before the formation of the first weld part104 so as to have a thickness for the development of an easydeformability adhering to the light-absorbable member 102. In order toensure the adhesiveness by sufficient deformation, the thickness of thelight-permeable member 106 is preferably 0.005 mm-0.2 mm, morepreferably 0.01 mm-0.1 mm considering the formability.

In order that the light-permeable member 106 is adhered to thelight-absorbable member 102 by deforming when the interior of theopening portion O is depressurized to not less than −80 kPa but not morethan −20 kPa as a gauge pressure before the formation of the first weldpart 104, it is preferable to select or use a material having a tensileelastic coefficient (Young's modulus) of 0.01-18 GPa. When the tensileelastic coefficient (Young's modulus) of the light-permeable member 106exceeds 18 GPa, it is necessary to make the thickness very thinner foreasily deforming in the depressurization of the opening portion O andhence it is difficult to shape the member as designed. For example, whenthe light-permeable member 106 is formed by injection molding, a resinis not flown into a thinned portion, which is a cause of poor formation.On the other hand, when the tensile elastic coefficient (Young'smodulus) of the light-permeable member 106 is less than 0.01 GPa, therigidity of the material itself becomes lower, and hence it is difficultto keep the shape of the member itself and it is difficult to place themember of the target shape in a target position. In order to balance theeasy deformability, formability and positioning property of thelight-permeable member 106 in a high dimension, it is preferable toselect or control the tensile elastic coefficient (Young's modulus) ofthe material for the light-permeable member 106 within a range of 6-10GPa. The tensile elastic coefficient (Young's modulus) can be measuredby placing a test specimen as described in JIS K7162 in a tensiontesting machine, drawing a stress-strain curve from stress and strain(deformation quantity) according to a definition of JIS K7161 anddetermining a gradient from the curve. In this case, if thestress-strain curve is not linear and it is difficult to determine thegradient therefrom, a secant modulus (a gradient of a straight lineconnecting a point of the stress-strain curve to an original point) orthe like can be used instead of the Young's modulus.

In the joint structure 100, a ratio of an area S2 of a portion at theside of the light-absorbable member 102 (a portion below a boundary faceF, which is called as a “second portion” hereinafter) to an are S1 of aportion at the side of the light-permeable member 106 (a portion above aboundary face F, which is called as a “first portion” hereinafter) inthe first weld part 104 is within a range of 12-35 viewing a sectionperpendicular to the extending direction of the first weld part 104 asshown by an enlarged view in FIG. 1B. When the ratio is less than 12,there is a fear of causing a separation starting a boundary to the weldpart 104 when a force peeling the light-permeable member 106 from thelight-absorbable member 102 is applied (boundary separation) or aseparation of at least a part of a portion of the weld part 104 at theside of the light-absorbable member 102 at a state of integrally unitingto the light-permeable member 106. Also, this separation is difficult tobe inspected non-destructively in an industrial production. When theratio of area S2 to area S1 is not less than 12, the separation ishardly caused in the weld part 104, and the light-permeable member 106or the light-absorbable member 102 itself is broken when a force peelingthe light-permeable member 106 from the light-absorbable member 102 isapplied (member breakage), so that it is enough to control strengths ofthe members 102 and 106 when the welding strength is designed or set andhence the structure can be manufactured stably. On the other hand, whenthe ratio exceeds 35, it is necessary to increase a power or prolong anirradiation time for arriving the laser beam at a deeper position of thelight-absorbable member 102, and hence there is a fear of exposingthermal influence to the light-permeable member 106 (upheaving,bubbling, melting on the surface, carbonization due to burning,discoloring) or thermal influence to the light-absorbable member 102(carbonization due to burning, bubbling). In order to realize theavoidance of these thermal influences and the suppression and preventionof the separation in the weld part 104 in a high dimension, the ratio ofS2 to S1 is preferable to be a range of 19-26.

When the ratio of the area S2 of the portion at the side of thelight-permeable member to the area S1 of the portion at the side of thelight-absorbable member in the first weld part 104 is made to the aboverange, the thermal influence to the light-permeable member associatedwith the formation of the first weld part 104 can be made small tosuppress thermal strain of the light-permeable member 106 while ensuringthe joining strength, and hence the more excellent adhesiveness betweenthe light-permeable member 106 and the light-absorbable member 102 bysuction can be obtained together with the adhesion effect by the easydeformation of the thin sheet-like light-permeable member 106.

Moreover, the first weld part 104 having the above ratio of area S2 toarea S1 can be formed by the method of manufacturing the joint structureas mentioned later with reference to FIGS. 8A-8D. In the measurement ofthe areas S1 and S2, the range (boundary) of the first weld part 104 canbe judged by cutting the joint structure 100 in a directionperpendicular to the extending direction of the first weld part 104 toprepare a test specimen and observing a section thereof with an opticalmicroscope or an electron microscope or confirming a tomographic imagethereof with an X-ray CT.

When the light-permeable member 106 is produced by injection molding,convex warping toward the lower face side or toward the upper face sideof the light-permeable member 106 may be generated resulting from theposition of the gate, flowing of the molten resin, non-uniform coolingafter the take-out from a mold and the like. The convex warping towardthe lower face side is unfavorable because a gap is caused between theperipheral edge portion of the light-permeable member 106 and the upperend face of the peripheral wall 108 of the light-absorbable member 102when the light-permeable member 106 is superposed on thelight-absorbable member 102. In this embodiment, therefore, a concaveportion 116 having a reduced thickness is formed in the lower face ofthe light-permeable member 106 (face at the side of the light-absorbablemember 102) over not less than 50% of the inner region of the first weldpart 104, whereby the warping direction is induced into a direction offorming convex toward the upper face side. When the forming region ofthe concave portion 116 is less than 50% of the inner region of thefirst weld part 104, there is a fear that a force enough to inducewarping of the light-permeable member 106 as a whole with respect toshrinking of the resin material causing the warping. In order to preventthe warping quantity from excessively increasing, it is preferable tomake the depth of the concave portion 116 to not more than 50% of thethickness. If the depth of the concave portion 116 exceeds 50% of thethickness, the rigidity of the light-permeable member 106 is decreasedto cause torsion as to the shrink of the resin material causing thewarping, so that a gap is generated between the light-permeable member106 and the light-absorbable member 102 in the adhesion by suction tomake adhesiveness poor and hence there is a fear of causing positionshift or poor welding (excessive temperature rise or unmelting due tonon-transfer of heat).

Another embodiment of the joint structure 200 according to the inventionwill be described with reference to FIGS. 2A, 2B and 2C. The jointstructure 200 is different from the joint structure 100 in a point thatplural opening portions O are formed in the light-absorbable member 202.

The light-absorbable member 202 is provided with a peripheral wall 208,a bottom wall 210 closing a lower end part of the peripheral wall 208,and a top wall 218 communicating to an upper end part of the peripheralwall 208, and plural slits 220 extending in the same direction areformed in the top wall 218 to define opening portions O. The top wall218 can prevent a light-permeable member 206 or weld parts 204, 214 frombreaking for controlling flexural deformation of the light-permeablemember 206 when shock or load is applied to the upper face of thelight-permeable member 206 from exterior. Since the top wall 218 acts asa beam, it can reinforce the peripheral wall 208 of the light-absorbablemember 202.

A concave portion 216 of the light-permeable member 206 has an effect ofcontrolling the warping direction and quantity of the light-permeablemember 206 as mentioned above. In addition to this, a gap is keptbetween the light-permeable member 206 and the top wall 218. As aresult, when the opening portion O is depressurized, the light-permeablemember 206 can be contacted with the top wall 218 to prevent thedecrease of an area receiving a negative pressure. If the area receivingthe negative pressure is decreased, the light-permeable member cannot bedeformed sufficiently under a vacuum pressure, and there is a fear ofdamaging an adhesiveness between the light-permeable member 206 and thelight-absorbable member 202 by suction. From a viewpoint of thisprevention, the forming region of the concave portion 216 constitutingthe light-permeable member 206 is preferable to be not less than 50% ofan interior region of the annular weld part 204.

Even in the joint structure 200, a ratio of an area S2 of a portion atthe side of the light-absorbable member 202 to an area S1 of a portionat the side of the light-permeable member 206 in the annular weld part204 viewing a section perpendicular to an extending direction thereof iswithin a range of 12-35, preferably 19-26 similarly in theaforementioned joint structure 100.

The other embodiment of the joint structure 300 according to theinvention will be described with reference to FIGS. 3A, 3B, and 3C. Thejoint structure 300 is provided with a light-permeable member 306 and alight-absorbable member 302. The light-absorbable member 302 has aperipheral wall 308, a bottom wall 310 closing a lower end part of theperipheral wall 308, and a top wall 318 communicating to an upper endpart of the peripheral wall 308. Plural slits 320 extending in the samedirection are formed in the top wall 318 to define opening portions O.The joint structure 300 is different from the joint structures 100 and200 in a point that a thinned piece 324 adhering to an upper face end ofa peripheral wall 308 of a light-absorbable member 302 is formed bydeforming a light-permeable member 306 at a position outside a firstweld part 304 before the formation of the first weld part 304 when aninterior of an opening portion O is at a depressurized state. Thus, evenwhen a gap is caused between the the upper end face of the peripheralwall 308 of the light-absorbable member 302 and the light-permeablemember 306 in the superposition between the light-permeable member 306and the light-absorbable member 302, the thinned piece 324 of thelight-permeable member 306 can be drawn and adhered to the upper endface of the peripheral wall 308 of the light-absorbable member 302 whenthe interior of the opening portion O is depressurized through a suctionport 312, so that vacuum breakage due to air leakage can be preventedand also an excellent adhesiveness between the light-permeable member306 and the light-absorbable member 302 by suction can be obtained.

To this end, the thinned piece 324 is preferable to be formed in athickness developing the easy deformability for adhering to thelight-absorbable member 302 by deforming when the interior of theopening portion O is depressurized to not less than −80 kPa but not morethan −20 kPa as a gauge pressure before the formation of the first weldpart 304. In order to ensure the adhesiveness by sufficient deformation,the thickness of the thinned piece is preferably 0.005 mm-0.2 mm, morepreferably 0.01 mm-0.1 mm in view of the formability.

In the example of FIGS. 3A 3B, and 3C, the thinned piece 324 is formedin a horizontal direction from the lower end of the peripheral portionof the light-permeable member 306 along the upper end face of theperipheral wall 308 of the light-absorbable member 302. Alternatively,it may be hanged down from the lower end of the peripheral portion ofthe light-permeable member 306 along the outer face of the peripheralwall 308 as shown in FIG. 4A or an annular groove 326 is formed in theupper end face of the peripheral wall 308 of the light-absorbable member302 and the thinned piece 324 may be hanged down from the lower face ofthe light-permeable member 306 so as to insert into the annular groove326 as shown in FIG. 4B.

Even in the joint structure 300, the annular weld part 304 is preferableto have a ratio of an area S2 of a portion at the side of thelight-absorbable member 302 to an area S1 of a portion at the side ofthe light-permeable member 306 viewing a section perpendicular to theextending direction thereof within a range of 12-35, more preferably19-26 similarly in the joint structures 100 and 200.

Next, the method of manufacturing the joint structure according to theinvention will be described with reference to FIGS. 5A, 5B, 6A, 6B, 7,8A-8D, and 9A-9C. Here, the method of manufacturing the joint structure100 shown in FIGS. 1A, 1B, and 1C are described as an example. Thismanufacturing method can be applied to the manufacture of the jointstructures 200 and 300 shown in FIGS. 2A, 2B, 3A, 3B, 4A and 4B.

The first step is a step of providing members. A light-absorbable member102 and a light-permeable member 106 are provided in this step. Thematerial and basic structure of each of the light-absorbable member 102and the light-permeable member 106 in the joint structure 100 arepreviously described with reference to FIGS. 1A, 1B, and 1C, so thattheir overlapping explanations are omitted here.

FIGS. 5A, 5B and 5C show the light-absorbable member 102 before thejoining to the light-permeable member 106, wherein FIG. 5A is a planeview, FIG. 5B is a section view taken along a line D-D of FIG. 5A, andFIG. 5C is enlarged view of region V-C in FIG. 5B. As shown in thisfigure, an annular groove 130 is previously formed in an upper end faceof a peripheral wall 108 of the light-absorbable member 102 (facecontacting to the light-permeable member 106) and at a predeterminedsite of forming a first weld part 104. The width of the annular groove130 is preferable to be made larger than a diameter of a laser beam tobe irradiated and is 0.1-3 mm. When the width of the annular groove 130is less than 0.1 mm, a width of the first weld part 104 to be formedtherein cannot be ensured sufficiently, and hence there is a fear thatthe welding strength is decreased and an airtightness or the like cannotbe maintained due to the penetration of air, water and dust by exteriorforce or change of pressure. When the width of the annular groove 130exceeds 3 mm, there is a fear that a portion other than the first weldpart 104 is thermally influenced and deformed by heat in the welding oran excessive strain is retained by heat shrinkage in the solidificationof the first weld part 104 to cause deformation. Also, the depth of theannular groove 130 (distance from a boundary face F to a groove bottom)is preferable to be not less than L/20 (mm) but not more than L (mm)when L is the width (mm) of the annular groove 130. Thus, as mentionedlater with reference to FIGS. 8A-8D, a laser beam can be irradiated tothe annular groove 130 to sufficiently expand a molten pool generated inthe groove bottom, while heat generated therein can be well transferredto the light-permeable member 106 to thereby form a good weld part 104.Moreover, the depth of the annular groove 130 is preferable to be notless than L/10 (mm) but not more than L/3 (mm) in view of ensuring thestrength and airtightness of the weld part 104. For example, the annulargroove 130 have a width L of 0.3 mm and a depth of 0.05 (=L/6) mm. Ifthe depth of the annular groove 130 is less than L/20 (mm), the expandedmolten pool contacts with the light-permeable member 106 just after theirradiation of the laser beam to the bottom of the annular groove 130,while heat is dispersed, so that the molten pool cannot be widened in alateral direction sufficiently and hence there is a fear that thewelding becomes poor (a part of the annular groove 130 is left). If thedepth of the annular groove 130 exceeds L (mm), the molten poolgenerated in the bottom cannot arrive at the light-permeable member 106though it is expanded, and hence there is a fear that carbonization dueto burning or discoloration is caused to bring about the poor welding.In the illustrated example, the sectional shape of the annular groove130 is rectangular, but may be semi-circular or semi-ellipsoidal.Furthermore, at least one communication groove 132 communicating theannular groove 130 to an interior of an opening portion O (4 grooves pereach side in the illustrated example) are previously formed in the upperend face of the peripheral wall 108.

The second step is a step of arranging the light-permeable member 106 onthe light-absorbable member 102 so as to cover the opening portion O asshown in FIG. 6A.

The third step is a step of adhering the superposed light-absorbablemember 102 and light-permeable member 106 to each other by suction,wherein the adhesion by suction is performed by depressurizing theinterior of the opening portion O. As a state after the superposition ofthe light-permeable member 106 and the light-absorbable member 102 isshown in a left of FIG. 6B, a gap may be formed between thelight-permeable member 106 and the light-absorbable member 102 due towarping in the formation of the light-permeable member 106 or the like.However, since the light-permeable member 106 is formed into a thinesheet, when the interior of the opening portion O is depressurized, theperipheral edge portion of the light-permeable member 106 can bedeformed so as to direct to the upper end face of the peripheral wall108 and adhered thereto as shown in a right of FIG. 6B.

The depressurization in the interior of the opening portion O can beperformed with an external pressure-controlling device D as shown inFIG. 7 and through a suction port 112 previously formed in thelight-absorbable member 102.

The pressure-controlling device D is comprised mainly of adepressurization device D1, a pressurization device D2, a controller D3and a double pipe P connected to the suction port 112.

The depressurization device D1 comprises a vacuum pump for dischargingair inside the opening portion O by suction and an electric leak valve(not shown). In a suction line L1 of the depressurization device D1 isdisposed a pressure sensor PG1, whereby a pressure inside the openingportion O can be detected during the depressurization.

The pressurization device D2 comprises a pressurized tank and a feedvalve for feeding a purge gas of air or an inert gas such as nitrogen,argon or the like (not shown). In a feed line L2 of the pressurizationdevice D2 is disposed a pressure sensor PG2, whereby a pressure insidethe opening portion O can be detected during the pressurization.

The controller D3 is constructed by PLC (programmable logic controller),a personal computer or the like, which adjusts an opening degree of thefeed valve and the leak valve. Also, the controller 3 is connected tothe pressure sensors PG1 and PG2, and the feed valve and leak valve canbe controlled based on signals detected by the pressure sensors PG1 andPG2.

The double pipe P is comprised of a suction pipe p1 arranged outside anda feed pipe p2 arranged inside. The suction pipe p1 is communicated withthe interior of the opening portion O and the depressurization device D1to suck air from the interior of the opening portion O. The feed pipe p2is communicated with the interior of the opening portion O and thepressurization device D2 to feed a purge gas to the interior of theopening portion O. Moreover, an outer pipe of the double pipe P may bethe feed pipe and an inner pipe thereof may be the suction pipe.

As shown in FIG. 7, the fourth step is a joining step wherein a laserbeam LB is irradiated from the side of the light-permeable member 106toward the upper end face of the peripheral wall 108 of thelight-absorbable member 102 at a state of adhering the light-absorbablemember 102 and the light-permeable member 106 by suction to form a firstweld part 104 and second weld parts 114 in the boundary face F betweenthe light-absorbable member 102 and the light-permeable member 106 or inthe vicinity thereof (see FIGS. 1A, 1B, and 1C) to thereby join thelight-absorbable member 102 and the light-permeable member 106 to eachother.

Even in this joining step, the interior of the opening portion O ismaintained at a depressurized state, but it is preferable to feed apurge gas to the interior of the opening portion O through the feed pipep2 at least during the formation of the first weld part 104. In thiscase, air flow can be generated inside the opening portion O, wherebysoot generated in the welding or vaporization ingredient of a flameretardant can be discharged and removed efficiently through the suctionpipe p1 toward exterior.

In the formation of the weld parts 104 and 114, the second weld parts114 are first formed and thereafter the first weld part 104 is formed.Because, the light-permeable member 106 is temporarily joined to thelight-absorbable member 102 through the second weld parts 114 beingrelatively small in the thermal load to the light-permeable member 106and then thermal deformation of the light-permeable member 106 issuppressed in the formation of the first weld part 104 being relativelylarge in the thermal load to prevent vacuum breakage due to air leakageresulted from this thermal deformation. Since the pressure receivingarea to vacuum is decreased with the advance of the formation of thefirst weld part 104, it is preferable to arrange three or more secondweld parts 114 on a plane for supplementing the decreased quantity ofthe pressure. In this example, four second weld parts are formed in thecorner portion of the light-permeable member 106.

The second weld parts 114 are formed by irradiating a laser beam LB tothe upper end face of the peripheral wall 108 of the light-absorbablemember 102 at a state of stopping an optical head H (FIG. 7) above thelight-permeable member 106. The second weld part 114 is preferable tohave a diameter of about 0.3-0.7 mm, more preferably about 0.5 mm. Thefirst weld part 104 is formed by irradiating a laser beam LB to theupper end face of the peripheral wall 108 while moving the optical headH along the peripheral wall 108 of the light-absorbable member 102 abovethe light-permeable member 106. The width of the first weld part 104 ispreferably about 0.3-0.7 mm, more preferably about 0.5 mm. As anoscillator of the laser beam LB can be used, for example, a fiber laser(wavelength: 1070 nm), a YAG laser (wavelength: 1064 nm), asemiconductor laser (wavelength: 808 nm, 840 nm or 940 nm), a CO₂ laser(wavelength: 10600 nm) and so on.

A process of forming the first weld part 104 in which a ratio of an areaof the second portion S2 to an area of the first portion S1 in FIGS. 1A,1B, and 1C are set to 12-35 by irradiating a laser beam LB to theannular groove 130 previously formed in the upper end face of theperipheral wall 108 of the light-absorbable member 102 will be describedwith reference to FIGS. 8A-8D.

When a laser beam is irradiated from the side of the light-permeablemember 106 toward the bottom of the annular groove 130 at a state ofadhering the light-absorbable member 102 and the light-permeable member106 to each other by suction as shown in FIG. 8A, the bottom of theannular groove 130 is melted by heat generation to start bubbling in amolten pool as shown in FIG. 8B. By continuously irradiating the laserbeam is grown bubbles to grow the molten pool as shown in FIG. 8C. Inthis case, the molten pool of the light-absorbable member 102 is notcontacted with the light-permeable member 106 due to the presence of theannular groove 130, so that the molten pool can be grown till sufficientwidth and depth are obtained. In FIG. 8D is shown a state that theirradiation of the laser beam is stopped to complete the formation ofthe annular weld part 104 after the arrival of the molten pool at thelight-permeable member 106.

In this example, a communication groove 132 communicating the annulargroove 130 to the opening portion O is disposed in the upper end face ofthe peripheral wall 108 of the light-absorbable member 102, so that sootgenerated in the process of forming the annular weld part 104 andvaporization ingredient v of a flame retardant are sucked and dischargedinto the opening portion O through the annular groove 130 and thecommunication groove 132 and finally discharged to exterior through thesuction pipe p1.

The fifth step is a step of inspecting an airtightness by conducting anairtight test of the first weld part 104 in which a pressure change perunit time is measured by keeping the depressurized state inside theopening portion O or pressurizing the interior of the opening portion Oor alternately performing the depressurization and the pressurization.The pressure inside the opening portion O is measured by the pressuresensors PG1 and PG2 shown in FIG. 7, and the pressure change per unittime is calculated in the controller D3 and can be output to ordisplayed in exterior. Alternatively, the airtight test of the firstweld part 104 can be performed by arranging a flow rate sensor (notshown) in the suction line L1 or the feed line L2 to measure a change ofa flow rate per unit time.

The sixth step (not shown) is a step of closing the suction port 112 byirradiating a laser beam LB from the side of the light-permeable member106 to the interior of the suction port 112 or surrounding thereof whilekeeping the depressurized state inside the opening portion O after theformation of the annular weld part 104. Thus, the interior of theopening portion O can be closed while keeping vacuum inside the openingportion O. Of course, the suction port 112 may be at an opened state.

According to the method of manufacturing the joint structure accordingto the invention, the opening portion O is formed in thelight-absorbable member 102, and the light-absorbable member 102 isadhered to the light-permeable member 106 by suction by depressurizingthe interior of the opening portion O, so that the use of the glassplate for adhering both the members 102 and 106 to each other under apressure is useless and the aforementioned various problems resultedfrom the use of the glass plate can be solved.

Since the light-permeable member 106 is temporarily joined to thelight-absorbable member 102 by forming the second weld parts 114 priorto the formation of the first weld part 104, warping resulted from theshaping of the light-permeable member 106 can be corrected and alsothermal deformation of the light-permeable member 106 can be suppressedon the way of forming the first weld part 104, so that the decrease ofthe adhesiveness by suction due to these warping and thermal deformationcan be prevented.

Further, the light-permeable member 106 can be deformed easily bydepressurizing the interior of the opening portion O, so that even ifthe gap is generated between the light-permeable member 106 and thelight-absorbable member 102 in the superposition, the gap can be closedwith the light-permeable member 106 by depressurizing the interior ofthe opening portion O and the excellent adhesiveness by suction can beobtained.

Since the annular groove 130 is formed on the upper end face of theperipheral wall 108 of the light-absorbable member 102 and the firstweld part 104 is formed by irradiating a laser beam LB to the annulargroove 130, a high joining strength can be obtained by the formation ofweld part 104 having sufficient width and depth, and also thermalinfluence upon the light-permeable member 106 can be made small tosuppress thermal deformation of the light-permeable member 106 in thewelding process and the decrease of adhesiveness by suction due to thethermal deformation can be prevented.

Since the communication groove 132 communicating the annular groove 130to the opening portion O is disposed in the upper end face of theperipheral wall 108 of the light-absorbable member 102, soot generatedduring the formation of the annular weld part 104 and vaporizationingredient v of a flame retardant can be sucked into the opening portionO through the annular groove 130 and the communication groove 132 andfinally discharged to exterior through the suction pipe p1.

Since the depressurization in the opening portion O is performed whilefeeding the purge gas to the interior of the opening portion O, air flowcan be generated in the opening portion O to discharge and remove thesoot and the vaporization ingredient v efficiently.

When the airtightness test of the first weld part 104 is performedkeeping the depressurized state of the opening portion O after theformation of the first weld part 104, or pressurizing the interior ofthe opening portion O, or alternately performing the depressurizationand the pressurization to measure a change of pressure or flow rate perunit time, the manufacturing installation ca be simplified and themanufacturing time can be shortened largely.

When the pressure in the opening portion O is always detected by thepressure sensor PG1 and the adhesion between the light-absorbable member102 and the light-permeable member 106, the start of forming the firstweld part 104 and the end of forming the first weld part 104 are judgedbased on the pressure change detected, it is possible to shorten workingtime in the usual production and early handling in the abnormal state.

Although the above is described with reference to the illustratedexamples, the invention is not limited to these examples and variousmodifications and additions may be performed within a scope described inclaims. In the method of manufacturing the joint structure of the aboveembodiments, the bottom of the annular groove 130 is illustrated to beflat, but an elevated portion 134 may be provided on the groove bottomas shown in FIG. 9A. Also, the number of the annular groove 130 is notlimited to one. For example, two adjoining grooves may be disposed andintegrally united in the welding to form a wider weld part 104 as shownin FIG. 9B, or an annular groove 136 may be disposed at the side of thelight-permeable member 106 as shown in FIG. 9C.

EXAMPLE Example 1

An example of applying the invention to a connector will be described.FIGS. 10A, 10B, and 10C show a connector using the joint structure 200of FIGS. 2A, 2B and 2C, in which FIG. 2A is a perspective view, FIG. 2Bis a section view along a fitting direction X, and FIG. 2C is enlargedview of region II-C in FIG. 2B. In this figure, the corresponding memberor portion is represented by adding ‘ to the symbol, and the overlappingexplanation is omitted.

This connector 200’ is a receptor connector fixed to a substrate in anelectronic device such as mobile device, information device or the likeand connected to another connector (not shown) by inserting in a fittingdirection X. This is comprised mainly of a housing 202′ as alight-absorbable member 202, plural contacts 203 extended in the fittingdirection X and arranged in a direction perpendicular to the fittingdirection X, and a thin sheet-formed cover 206′ as a light-permeablemember 206 sealed so as to cover an opening portion O′ of the housing202′.

The housing 202′ is made from a light-absorbable and insulatingthermoplastic resin and provided with a peripheral wall 208′ having afitting port 212′ for inserting the other connector, a bottom wall 210′and a top wall 218′.

In the top wall 218′ of the housing 202′ are formed a plurality of slits220′ along the fitting direction X, and the opening portion O′ isdefined by these slits 220′. In each of the slits 220′ is arranged thecontact 203. The forward end of the each contact 203 is protrudeddownward from the inner face of the top wall 218′ for connecting to theother connector, while the posterior end thereof is exposed from thehousing 202′ for connecting to the substrate of the electronic device orthe other printed circuit board.

The cover 206′ is superposed to the housing 202′ so as to cover theopening portion O′ of the housing 202′ and joined to the upper end faceof the peripheral wall 208′ over the whole periphery through a firstannular weld part 204′ formed so as to enclose the slits 220′ in abundle. Thus, a root of penetrating air, soot or water from a fittingport 212′ through the slits 220′ into the interior of the electronicdevice is blocked by the cover 206′ and the first weld part 204′. Also,four dot-like second weld parts 214′ are formed outside the first weldpart 204′ and adjacent to corner parts of the cover 206′.

In the connector 200′, the annular weld part 204′ has a ratio of an areaS2′ of a portion at the side of the housing 202′ to an area S1′ of aportion at the side of the cover 206′ viewing from a sectionperpendicular to the extending direction within a range of 12-35,preferably 19-26. The symbol F′ in FIG. 10B represents a boundary facebetween the housing 202′ and the cover 206′.

The connector 200′ can be manufactured by the method described withreference to FIGS. 5A, 5B, 6A, 6B, 7, and 8A-8D using the fitting port212′ as a suction port 212.

Example 2

An example of applying the invention to a sensor will be described.FIGS. 11A, 11B, and 11C show a sensor using the joint structure 300shown in FIGS. 4A and 4B, in which FIG. 4A is a perspective view andFIG. 4B is a section view.

The sensor 300′ may be all types of acceleration sensor, vibrationsensor, angular velocity sensor, distance sensor, position sensor and soon. The sensor 300′ is comprised mainly of a chassis 302′ as alight-absorbable member 302, and a cover 306′ as a light-permeablemember 306 sealed so as to cover an opening portion O′ of the chassis302′. A detector body (sensor chip, not shown) is housed in the interiorof the chassis 302′.

The chassis 302′ is made from a light-absorbable thermoplastic resin andprovided with a peripheral wall 308′ defining the opening portion O′ andprotruding a suction cylinder 312′ forward and a bottom wall 310′.

The cover 306′ is placed on the peripheral wall 308′ of the chassis 302′so as to cover the opening portion O′ of the chassis 302′ and joinedthereto over the whole periphery through first annular weld part 304′and second dot-like weld parts 314′. In the peripheral edge part of thecover 306′ is hanged down a thinned piece 324′ along the outer face ofthe peripheral wall 308′. The thinned piece 324′ is formed so as to drawand adhere to the peripheral wall 308′ when the interior of the openingportion O′ is depressurized through the suction cylinder 312′.

In the sensor 300′, the annular weld part 304′ has a ratio of an areaS2′ of a portion at the side of the chassis 302′ to an area S1′ of aportion at the side of the cover 306′ viewing from a sectionperpendicular to the extending direction within a range of 12-35,preferably 19-26. The symbol F′ in FIG. 11B represents a boundary facebetween the chassis 302′ and the cover 306′.

The sensor 300′ can be manufactured by the method described withreference to FIGS. 5A, 5B, 6A, 6B, 7, and 8A-8D using the suctioncylinder 312′ as a suction port 312.

Moreover, the base end part of the suction cylinder 312′ is opened, butthe opening of the base end part of the suction cylinder 312′ may beclosed by irradiating a laser beam to the vicinity of the opened baseend part of the suction cylinder 312′ from the cover 306′ at a state ofkeeping the depressurization of the opening portion O′ after theformation of the annular weld part 304′. Thus, the interior of thesensor 300′ can be closed at a state of keeping vacuum.

INDUSTRIAL APPLICABILITY

According to the invention, the joint structure suitable for adheringmutual members to be joined to each other uniformly and surely isprovided without using a glass plate, and also the method ofmanufacturing a joint structure, which is capable of adhering mutualmembers to be joined to each other uniformly and surely, can be providedwithout using a glass plate.

DESCRIPTION OF REFERENCE SYMBOLS

-   -   100, 200, 300 joint structure    -   102, 202, 302 light-absorbable member    -   104, 204, 304 annular weld part (first weld part)    -   106, 206, 306 light-permeable member    -   108, 208, 308 peripheral wall    -   112, 212, 312 suction port    -   114, 214, 314 dot-like weld part (second weld part)    -   324 thinned piece    -   D pressure control device    -   D1 depressurization device    -   D2 pressurization device    -   D3 controller    -   F boundary face    -   H optical head    -   L1 suction line    -   L2 feed line    -   O opening portion    -   PG1, PG2 pressure sensor    -   S1 area of first portion of annular weld part (at the side of        light-permeable member)    -   S2 area of second portion of annular weld part (at the side of        light-absorbable member)

What is claimed is:
 1. A joint structure comprising a light-absorbablemember having at least one opening portion and a light-permeable membersuperposed on the light-absorbable member so as to cover the openingportion, wherein an annular first weld part is formed so as to enclosethe opening portion and join an end face of a peripheral wallsurrounding the at least one opening portion of the light-absorbablemember to the light-permeable member, and a dot-like second weld part(s)joining the light-absorbable member and the light-permeable member isformed in a position adjacent to the annular first weld part, whereinthe light-permeable member has a substantially rectangular shape, andthe dot-like second weld part is formed adjacent a corner of thesubstantially rectangular shape.
 2. The joint structure according toclaim 1, wherein the light-permeable member is formed into a thin sheetadhering to the light-absorbable member by deforming at a depressurizedstate of an interior of the opening portion before the formation of theannular first weld part.
 3. The joint structure according to claim 2,wherein the light-permeable member is formed to have a thicknessadhering to the light-absorbable member by deforming when the interiorof the opening portion is depressurized to not less than −80 kPa but notmore than −20 kPa as a gauge pressure before the formation of theannular first weld part.
 4. The joint structure according to claim 1,wherein the light-permeable member is provided outside the annular firstweld part with a thinned piece adhering to the light-absorbable memberby deforming at a depressurized state of an interior of the openingportion before the formation of the annular first weld part.
 5. Thejoint structure according to claim 4, wherein the thinned piece isformed in a thickness adhering to the light-absorbable member bydeforming when the interior of the opening portion is depressurized tonot less than −80 kPa but not more than −20 kPa as a gauge pressurebefore the formation of the annular first weld part.
 6. The jointstructure according to claim 4, wherein the thinned piece is formedalong a peripheral edge part of the light-absorbable member.